In high-proportion new energy power systems, virtual synchronous control (VSG) is used as a key technology to enhance system inertia and damping support. When applied to doubly-fed induction generators (DFIG), it profoundly changes the impedance characteristics of the system in the sub-synchronous and super-synchronous bands by establishing a complete sequential impedance model that takes into account the dynamic and frequency coupling of VSG. VSG-DFIGThe analysis reveals that the virtual rotor dynamics of the VSG supplant the traditional phase-locked loop (PLL), becoming the dominant mechanism for frequency coupling between the positive and negative sequences. This study establishes a rigorous framework for optimizing control parameters and evaluating oscillation risks in VSG-DFIG systems using a combination of analytical modeling and validated simulations.

virtual synchronous control, doubly-fed fan, frequency coupling, sequential impedance modeling, sub-synchronous oscillation